Fix MemoryError on get_input_media(game)

Because an integer was being passed where a TLObject was expected,
so the serialization with bytes() was actually requesting that many
bytes as opposed to properly converting the expected object.

tests/telethon/test_utils.py

@@ -0,0 +1,18 @@
+from telethon import utils
+from telethon.tl.types import (
+    MessageMediaGame, Game, PhotoEmpty
+)
+
+
+def test_game_input_media_memory_error():
+    large_long = 2**62
+    media = MessageMediaGame(Game(
+        id=large_long,  # <- key to trigger `MemoryError`
+        access_hash=large_long,
+        short_name='short_name',
+        title='title',
+        description='description',
+        photo=PhotoEmpty(large_long),
+    ))
+    input_media = utils.get_input_media(media)
+    bytes(input_media)  # <- shouldn't raise `MemoryError`